Abstracts - Deutsche Zoologische Gesellschaft

Plenary Lecturesduring insect evolution. Thus, to obtain a correct (=complete) understanding of insect endocrinology,genome-wide inventories of all insects with a sequenced genome must be carried out.L PL.1 (Su) - ENEvolution of cerebral cortical developmentZoltán MolnárDepartment of Physiology, Anatomy and Genetics, University of Oxford, UKThis review aims to provide examples of how both comparative and genetic analyses contribute toour understanding of the rules for cortical development and evolution. Genetic studies have helpedus to realize the evolutionary rules of telencephalic organization in vertebrates. The control of the establishmentof conserved telencephalic subdivisions and the formation of boundaries between thesesubdivisions has been examined and the very specific alterations at the striatocortical junction havebeen revealed. Comparative studies and genetic analyses both demonstrate the differential origin andmigratory pattern of the two basic neuron types of the cerebral cortex. GABAergic interneurons aremostly generated in the subpallium and a common mechanism governs their migration to the dorsalcortex in both mammals and sauropsids. The pyramidal neurons are generated within the corticalgerminal zone and migrate radially, the earliest generated cell layers comprising preplate cells. Reelin-positiveCajal-Retzius cells are a general feature of all vertebrates studied so far; however, thereis a considerable amplification of the Reelin signalling with cortical complexity, which might havecontributed to the establishment of the basic mammalian pattern of cortical development. Based onnumerous recent observations we shall present the argument that specialization of the mitotic compartmentsmay constitute a major drive behind the evolution of the mammalian cortex. Comparativedevelopmental studies have revealed distinct features in the early compartments of the developingmacaque brain, drawing our attention to the limitations of some of the current model systems forunderstanding human developmental abnormalities of the cortex. Comparative and genetic aspectsof cortical development both reveal the workings of evolution. Supported by MRC and BBSRC.L PL.2 (Mo) - ENEvolution of morphological patterns in vertebrates viewed from developmentalperspectivesShigeru KurataniLaboratory for Evolutionary Morphology, RIKEN Center for Developmental Biology, JapanBy choosing a lamprey species Lethenteron japonicum, the evolutionary sequence of gnathostomeswas studied. As a basic developmental program, the lamprey head mesoderm is not segmented,but secondarily regionalized by pharyngeal pouches and otocyst, into several domains seen in gnathostomes;vertebrates appears to have evolved with somitomerism and branchiomerism that aredecoupled from each other, of which the latter became conspicuous with incorporation of the neuralcrest-derived ectomesenchyme by the absence of the former. The cephalic Hox code in the pharyngealarches (PAs), is partially conserved between the lamprey and gnathostomes, including the Hoxcode-default state in PA1 as the ground state of vertebrate branchiomerism. The gnathostome-specificjaw differentiation thus appears to have been obtained upon this shared developmental schemefor the PA positional values. Dlx genes, on the other hand, did not show clearly nested patterns ofexpression, suggesting that the Dlx code could be a comparatively a new feature for gnathostomes.